1. Field of the Invention
The present invention relates to a control apparatus for a fuel cell vehicle and to a control method for a fuel cell vehicle.
Priority is claimed on Japanese Patent Application No. 2005-169541, filed Jun. 9, 2005, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, in a fuel cell system in which, for example, fuel cells and secondary batteries connected in parallel serve as a power source relative to loads such as a motor for vehicle travel, a fuel cell system which restricts power supply to the load according to a residual capacity of the secondary batteries is already known (for example, see patent document 1).
Additionally, in a control apparatus for a fuel cell vehicle where, for example, fuel cells and secondary batteries connected in parallel serve as a power source relative to loads such as a motor for vehicle travel, a control apparatus for a fuel cell vehicle which restricts power supply to the load according to the maximum power generation volume of the fuel cells and a residual capacity of the secondary batteries, and which controls the regenerative operation of the motor for vehicle travel is already known (for example, see patent document 2).
Additionally, in a control apparatus for a fuel cell vehicle where, for example, fuel cells and secondary batteries connected in parallel serve as a power source relative to a load such as a motor for vehicle travel, a control apparatus for a fuel cell vehicle which restricts a power supply to the load according to the output voltage of the fuel cells and a maximum voltage of the secondary batteries is already known (for example, see patent document 3).
Patent document 1: Japanese Unexamined Patent Application, First Publication No. Hi0-74533.
Patent document 2: Japanese Unexamined Patent Application, First Publication No. 2003-79007.
Patent document 3: Japanese Unexamined Patent Application, First Publication No. 2004-185820.
With the fuel cell system and control apparatus relating to conventional technology mentioned above, the power supply to a motor used to operate a vehicle is controlled corresponding to the power which can be output from a power source formed by a fuel cell and a secondary battery. Therefore, for example, by establishing the upper limit of power which can be output from a power source corresponding to the temperature of the fuel cell or the secondary battery, the actual power consumed by the motor used to operate the vehicle is detected, corresponding to a detected value of an appropriate ammeter and voltage meter, and if it is detected that the actual power exceeds the upper power limit, then the power supply to the motor operating the vehicle is restricted.
However, when tires slip on a road surface which has a relatively low frictional resistance due to rainfall, freezing or the like, there is a case in which the output of the vehicle suddenly increases. In this case, the upper power limit is generated from the power source while detecting the actual current power consumed by the motor and restriction of the supply of the electronic power to the motor for driving the vehicle is started. Therefore, the system voltage of the fuel cell system is lowered excessively and the fuel cell and the secondary battery are not appropriately protected.
Concerning such problems, if, for example, as a determination threshold value relating to the actual electric power of a motor used to operate a vehicle, a value is established which is lower by a specific value than the upper power limit which can be output from the power source, even at a time prior to reaching the actual electric power of the motor used to drive a vehicle, at the point in time when the actual electric power reaches the specified determined threshold value, the restriction of the power supply to the motor used to drive the vehicle commences. In this case, there is the problem of excessively restricting the motor output used to drive the vehicle.
The present invention considers these circumstances, and has the objective of providing a control apparatus for a fuel cell vehicle and a control method for a fuel cell vehicle which can prevent excessively restricting the motor output used to drive a vehicle, as well as the excessive reduction of the system voltage of the fuel cell system.